Radio frequency identification devices (RFID's) are commonly utilized for electronically identifying objects. In an exemplary application, a transponder unit is attached to an object which is to be identified. The transponder unit is incorporated into a passive, readonly RFID system which comprises an interrogator used in conjunction with the transponder. The interrogator provides a carrier signal which powers (stimulates) the transponder and causes a signal to be transmitted from the transponder. The signal comprises data which identifies the object associated with the transponder. The signal is received by the interrogator, which is in data communication with a processing system configured to decode and interpret the data.
The interrogator commonly uses a coil antenna to stimulate the transponder. Such coil antenna consists of one or more coils of conductive material provided within a single plane, and can be in the form of, for example, a loop antenna. The transponder will frequently comprise a parallel resonant LC circuit, with such circuit being resonant at a carrier frequency of the interrogator. The transponder can also comprise a coil antenna.
An exemplary application of a passive, read-only RFID system is for identification of individual animals in a meat-processing plant. A reason for identifying individual animals in a meat-processing plant is to improve meat quality and/or farming processes. For instance, in modern farming practices it is desirable to track an animal throughout its entire lifetime up to, and including, slaughter to aid in understanding the factors that influence meat quality. To accomplish such tracking, an RFID transponder tag can be placed in an animal's ear at time of birth, and utilized to document events occurring within the animal's life. For instance, the RFID transponder can be utilized with interrogators to catalog the feed ingested by the animal, vaccinations provided to the animal, and any growth hormones administered to the animal. The transponder can further be utilized in combination with an interrogator at time of slaughter to catalogue the meat quality of the animal. Transponders can be utilized to track many (or even all) of the individual animals of a population, and information accumulated by the transponders can be studied to relate the effect, if any, of particular farming practices on meat quality.
In another exemplary use of a RFID in a meat-processing plant, transponders are provided on individual animal bodies within the plant to enable tracking of the bodies during processing to enable, for example, meat products from a particular body to be pulled in the event the body is found to be contaminated or diseased.
An exemplary system for utilizing passive, read-only RFID for identification and tracking of individual animals in a meat-processing plant is described with reference to FIGS. 1 and 2. Referring to FIG. 1, an interrogator 10 comprises a signal processing unit 12 and a planar coil antenna 14 electrically connected with processing unit 12. An animal body 16 (shown as a cow) is hung from a rail 18 and guided past antenna 14. A transponder 20 is attached to the animal body (specifically, transponder 20 is attached to an ear of the cow 16 in the shown embodiment). Transponder 20 comprises a planar coil antenna 22 (not visible in the view of FIG. 1, but shown in FIG. 2) which is configured as an inductive portion of a parallel resonant LC circuit. As animal body 16 passes antenna 14, transponder 20 is stimulated by a field (generally a magnetic field) established by antenna 14. The stimulated transponder then emits data which is received by interrogator 10 and subsequently processed to identify animal body 16. It is noted that the shown methodology of hanging the animal body from a rail is but one of many methodologies which can be utilized for transporting the animal bodies past antenna 14. Other methodologies include, for example, carting the animal bodies.
FIG. 2 illustrates an identical application as that of FIG. 1, with the difference that at least a portion of animal body 16 has swivelled relative to the orientation shown in FIG. 1. Accordingly, whereas the transponder of coil 22 of FIG. 1 is contained within a plane that is substantially parallel to the plane of antenna coil 14, the transponder coil 22 of FIG. 2 is contained within a plane that is substantially perpendicular to the plane of antenna 14. A difficulty with the processing shown in FIGS. 1 and 2 is that while the orientation shown in FIG. 1 results in good induction of a current in transponder 20 from the magnetic field of antenna 14, the orientation of FIG. 2 results in little or no induction. In fact, it is found that if transponder coil 22 is within a plane that is tilted more than about 27.degree. from parallel with a plane comprising antenna coil 14, there will be little or no data transfer from transponder 20 to antenna 14.
It would be desirable to develop alternative RFID systems which avoid at least some of the problems associated with the orientation dependencies of transponder 20 relative to antenna 14.